Does music break the mind-body connection?

"I've got it figured out," said Unruh. "Usually, every song lasts about four minutes. I run a mile in a little over eight. So if I can get through two songs, I know I'm a mile though my run."

Gyms are jammed with people like Unruh - the guy on the treadmill watching ESPN, the aerobic class bouncing to "Hollaback Girl," the spinner reading Self magazine. Words, images and especially songs can provide inspiration for exercisers, as well as a distraction from tedium and discomfort.

But are those distractions good or bad for exercisers? Researchers say it cuts both ways. Yes, a dose of video or audio can inspire better workouts. But distractions can also hurt performance.

In a way, music can add some static to the mind-body connection.

Since the dawn of the Walkman, headphones have been as important as sneakers to many exercisers. In a 2005 study, British researchers put 18 undergraduates on stationary bicycles to pedal either to silence or to "popular electronic dance music" on headphones. Participants worked about 13 percent harder to the up-tempo music compared to silence. One of the researchers, Sam Carr, suggested in an e-mail interview that music competes with an exercisers' awareness of how hard they're breathing, or how much their legs ache.

Still, athletes digging deep for peak performance would do well to ditch the headphones and focus on their bodies. Studies have shown that the more distracted the athlete, the slower the times, said Ohio University psychology professor Benjamin Ogles.

"If you want to maintain a high level of intensity, you pretty much have to focus on your body," he said.